It is now possible to image acute myocardial infarcts using 99mTc-chelates. Because all the present agents have shortcomings in terms of uptake in surrounding tissues or delayed blood clearance, part of this proposal is devoted to the synthesis and testing of radiopharmaceuticals based on their ability to chelate calcium and bind tissue sulfhydryl groups. The newly synthesized compounds will be screened in a simple rodent model and the promising agents will be tested in a canine heart prepared with external and internal coronary artery occlusion. The latter model will permit correlation with electrophysiologic, histologic and biochemical data and regional blood flow. The behavior of the most effective agents will be studied in man. Time-intensity-size relationships will be determined by sequential scintigraphy in patients with acute myocardial infarction. The effect of intervention procedures (e.g., hyaluronidase, intra-aortic balloon counter-pulsation, and beta blocking agents) on infarct size will then be assessed by comparing groups of patients with and without relevant therapies.